function animate(obj,target,callback){
    clearInterval(obj.timer);
    obj.timer = setInterval(() =>{
        if(obj.offsetLeft == target){
            clearInterval(obj.timer);
            // 判断函数是否存在
            if(callback != null){
                callback();
            }
            return;
        }
         // 步长 = (目标距离 - 当前距离) / 10
        var step = (target - obj.offsetLeft) / 10;
        setp = step > 0 ? Math.ceil(step) : Math.floor(step);
        obj.style.left = obj.offsetLeft + step + 'px';
    },50);
}